1. Field of the Invention
The present invention relates to a base isolation device used for the purpose of absorbing a quake of the ground by, for example, an earthquake to thereby reduce the quake of a building, or used for the purpose of reducing a quake applied to a precision machinery and tool in transportation etc. of the precision machinery and tool.
2. Description of the Related Art
Hitherto, as an earthquake countermeasure for real estates such as buildings and houses, or as a vibration countermeasure when carrying the precision machine and tool, a case of art work, and the like, there has been used a base isolation device for absorbing the vibration of the ground or a floor to thereby reduce it. As this base isolation device, there have been hitherto known one of a type in which rubber plates are laminated between a basement such as the ground and a structure body such as a construction object, one in which low friction slide faces consisting of fluororesin etc. are formed between the basement and the structure body, and the like.
However, in recent years, as a new base isolation device, there is proposed a base isolation device utilizing linear guide units used in a work table etc. of machine tool (Japanese Patent Laid-Open No. 240033/1996 Gazette). As shown in FIG. 14, this base isolation device comprises 1st and 2nd track rails 102, 103 in which rolling faces for rolling bodies such as balls are formed along longitudinal directions and which are fixed so as to be mutually orthogonal to a basement 100 and a structure body 101 respectively, a 1st slide member 104 incorporated to the 1st track rail 102 through many rolling bodies and freely linearly movable in reciprocation along the 1st track rail 102, and a second slide member 105 fixed to the 1st slide member 104, incorporated to the 2nd track rail 103 through many rolling bodies and freely linearly movable in reciprocation along the 2nd track rail 103, and it is adapted such that, if the basement 100 quakes by the earthquake and the like, the track rails 102, 103 and the slide members 104, 105 incorporated to the formers perform relative linear reciprocation motions.
FIG. 15 is a schematic view in case where a concrete use method of this base isolation device is seen from above. On the basement 100, the base isolation devices mentioned above are used in four places, and the 1st track rail 102 of each base isolation device is fixed to the basement 100 along an X-direction. On the other hand, the 2nd track rail 103 is fixed to the structure body (not shown) along a Y-direction orthogonal to the 1st track rail 102. Since a dynamic frictional coefficient between the track rails 102, 103 and the slide members 104, 105 is very small, if the basement 100 quakes in a horizontal direction by the earthquake and the like, the slide members 104, 105 of each base isolation device move on the track rails 102, 103 along the X-direction or the Y-direction to absorb the quake. That is, the structure body provided on the base isolation devices is insulated from the quake of the basement 100 and becomes such a state that as if it floats in the air. It is considered that the structure body violently quakes by the earthquake and the like because a period of the quake of the basement agrees with that of the quake of the structure body, thereby generating a resonance phenomena. However, in case where the structure body is insulated from the basement by the base isolation devices in this manner, since it is possible to avoid a generation of the resonance by setting the period of the quake of the structure body sufficiently large, it becomes possible to reduce the quake of the structure body.
On the other hand, although this base isolation device prevents the resonance between the basement and the structure body, since it is not one capable of completely preventing the quake of the structure body and, moreover, since it is one insulating the quake of the basement from that of the structure body as mentioned above, it follows that the quake remains after the earthquake for instance has quieted down. Therefore, when supporting the structure body by using such base isolation devices, as shown in FIG. 15 it has been necessary to provide damping units 106 between the basement 100 and the structure body separately from the base isolation devices to thereby absorb an energy of the quake of the structure body such that the quake quits down in short time. Hitherto, as such a damping unit, there have been known one adapted such that the basement and the structure body are connected by a rubber cylinder body formed by means of laminating alternately rubber plates and reinforcing plates, and a quake energy of the structure body is converted into a thermal energy accompanying with a shearing deformation of the rubber cylinder body, thereby absorbing the quake energy, and the like.
However, with this damping unit, since a shearing deformation amount of the rubber cylinder body connecting the basement and the structure body cannot be set large, it becomes a result that the damping unit limits movements in XY-directions in the base isolation device. Accordingly, in case where the above damping unit is used in combination with the base isolation device utilizing linear guide units, it becomes impossible to completely insulate the structure body from the basement, so that it becomes impossible to sufficiently absorb the quake of the basement by the base isolation device. Further, if the damping unit is provided separately from the base isolation device, there has been such a problem that an excessive labor is required correspondingly, and a work for providing the structure body on the basement in the base isolation device becomes complex.
The invention was made in view of such a problem, and its object is to provide a base isolation device with damping mechanism, which can effectively absorb a quake of a basement by insulating a structure body from the basement, and can intend to simplify an attaching work to the basement and the structure body.
That is, the invention is a base isolation device with damping mechanism, which is disposed between a basement and a structure body arranged on the basement and suppresses a transmission of a quake from the basement to the structure body, characterized by comprising: 1st and 2nd track rails formed with ball rolling faces along a longitudinal direction and disposed orthogonally to each other; a 1st slide member incorporated to the 1st track rail through many balls and freely linearly movable in reciprocation along the 1st track rail; a 2nd slide member connected to either of the 1st track rail or the 1st slide member, incorporated to the 2nd track rail through many balls and freely linearly movable in reciprocation along the 2nd track rail; motion conversion means which has a rotation transmission body arranged such that its axis agrees with a moving direction of the 1st slide member or the 2nd slide member, and converts a linear reciprocation motion of the slide member into a normal/reverse rotary motion of the rotation transmission body; a rotary sleeve connected to the rotation transmission body; a stationary sleeve accommodating the rotary sleeve and forming an action chamber of damping force between it and the rotary sleeve; and a viscous fluid sealed in the action chamber.
The base isolation device of the invention constituted in this manner is used under a state that, for example, the 1st track rail is fixed to the basement, while the structure body is fixed to the 2nd track rail orthogonal to the 1st track rail, and the 1st slide member and the 2nd slide member moving along the 1st and 2nd track rails are mutually fixed. On this occasion, the motion conversion means for converting the linear reciprocation motion of the slide member into the normal/reverse rotary motion, for example a ball screw unit, is connected to the 1st slide member or the 2nd slide member and, if the 1st slide member or the 2nd slide member is moved on the track rail with a quake of the basement, the rotation transmission body provided in the motion conversion means is rotated and, further, the rotary sleeve connected to the rotation transmission body is rotated. The rotary sleeve is accommodated in the stationary sleeve to thereby form the action chamber, and the viscous fluid is sealed in the action chamber. Accordingly if the rotary sleeve is rotated, a shearing frictional force is applied to the viscous fluid in the action chamber, so that a kinetic energy of the rotary sleeve is consumed as a thermal energy of the viscous fluid. In other words, it follows that an energy of the linear reciprocation motion of the slide member is consumed by the viscous fluid as the thermal energy, so that it is possible to reduce the motion of the slide member with respect to the track rail and, in turn, the motion of the structure body with respect to the basement.
Here, since the motion conversion means connected to the slide member merely converts the linear reciprocation motion into the rotary motion, it does not limit the motion of the slide member at all, so that the base isolation device of the invention can effectively absorb the quake of the basement. Further, since the rotary sleeve functioning as a damping unit is directly fixed to the slide member through the motion conversion means, when providing the structure body to the basement, it is unnecessary to provide the damping unit separately from the base isolation device, so that a work for arranging the structure body can be simplified correspondingly.